Modified carboxyalkyl cellulose



MODIFIED CARBOXYALKYL CELLULOSE Harry Weisberg, New York, N.Y., assignor to Londat Aetz Fabric C0., Elizabeth, N.J., a corporation of New Jersey No Drawing. Application September 30, 1955 Serial No. 537,877

7 Claims. (Cl. 260-232) This invention relates to modified carboxyalkyl cellulose products and methods of making the same.

Carboxyalkyl cellulose ethers such as sodium carboxymethyl cellulose, have varying solubility characteristics in respect to aqueous solutions of sodium hydroxide or other strong alkaline solvents, as the number of cal-boxymethyl units per anhydroglucose unit, changes. Furthermore, as the degree of substitution increases, the carboxymethyl cellulose becomes soluble in water.

An object of this invention is to provide a modified form of carboxymethyl cellulose which may have a degree of substitution extending over a wide range of values, yet each of such cellulose products will exhibit a uniformly high rate of solubility in aqueous solutions of sodium hydroxide of very low, as well as relatively high, concentrations.

Known forms of carboxymethyl cellulose with lower degrees of substitution, dissolve in alkaline solutions to a certain extent, but such solution is accompanied by the formation of gummy or gel-like residues which have the effect of retarding or otherwise adversely affecting the overall solubility of the carboxymethyl cellulose in the alkaline medium.

Such solubility characteristic is particularly disadvantageous when the carboxymethyl cellulose takes the form of a backing fabric used in lace manufacture. Here, the lace is stitched on the backing fabric and the composite product is placed in an alkaline bath to dissolve the backing fabric and release the lace therefrom. The gummy residues not only slow up the dissolution of the backing fabric, but additionally, deposit on the lace, requiring subsequent removal therefrom.

Accordingly, a further object of this invention is to provide carboxymethyl cellulose which has been chemically modified to give an end product which dissolves readily and quickly in aqueous alkaline solutions, leaves no gummy or gel-like residues and allows laces which may be associated with the modified carboxymethyl cellulose to be removed from the dissolving solutions free of objectionable coatings.

Another object of this invention is to provide modified cellulose products of the character described, which are economical to manufacture, do not require reagents of extreme toxicity in their formation, and do not require etherifying agents which will increase the flammability of the end product.

Still another object of this invention is to convert cellulose in various forms thereof including fiber, linters, thread, fabrics and felts, pulp and the like, into carboxymethyl ethers, which in turn, are further treated with chromic or periodic acids; the acid treatment leaving the original physical form of the cellulose unchanged and with a retention of a substantial portion of the tensile strength of the cellulose.

Still a further object of this invention is to provide a cotton fabric which is converted in situ to carboxymethyl cellulose and further modified to make the same particularly useful as a backing fabric on which laces may trite-d States Patent be stitched, such converted and modified fabric being readily handled in the lace making and associated machines, the composite structure so formed being passed through alkaline dissolving baths whereby the backing fabric will dissolve quickly in the bath to release the lace structure in clean form, free of any adherent gummy residues from the bath.

It has been found that cellulose, in the various forms thereof, which has been initially converted to carboxymethyl cellulose by the conventional use of sodium hydroxide and chloracetic acid or one of its soluble salts, in either order, as typically described in Patents 2,236,545 and 2,278,612; may be further treated with chromic or periodic acid under conditions which leave the end product with the original physical form of the cellulose unchanged, retaining a substantial portion of the strength of the cellulose, yet enhancing the solubility characteristics of such end product, as indicated above.

Such acid treatment may be applied to carboxymethyl cellulose having a degree of substitution ranging from about 0.02 to about 2.5. In the case of carboxymethyl celluloses having a degree of substitution of about 0.2 or higher, which have varying degrees of solubility in water, it is preferred that such etheritied products be converted to a water insoluble form such as the free acid or metal salts thereof including copper, lead, iron, silver or mercury salts of carboxymethyl cellulose, by procedures well known in the art.

The following examples illustrate the invention:

Example 1 Woven cotton fabric in the form of greige goods was soaked for about 2 minutes at room temperature in a 15% aqueous solution of chloracetic acid containing 0.5% of Naeconol NR which is a well known wetting agent and serves to facilitate the acid impregnation of the fabric. The thus treated fabric was then squeezed and placed in a 50% aqueous solution of sodium hydroxide for about 45 seconds at 77 C. and thereafter removed from the alkali and washed with water. The treated fabric was then passed through a dilute acid bath such as hydrochloric acid or the like, to sour the residual alkali in the treated material, and again washed with water. The resultant sodium carboxymethyl cellulose, in fabric form, showed a degree of substitution of 0.10.

The thus etherified fabric was further treated with an aqueous solution containing by weight 3.0% sodium bichromate and 4.0% concentrated sulfuric acid, for about 80 seconds at 76 C., leaving the physical form of the fabric unchanged and retaining a substantial amount of the strength of the original fabric. The acid treated fabric was thoroughly washed with water and dried. The acid treated fabric was then placed in a boiling 8% aqueous solution of sodium hydroxide, showing rapid solubility. On filtering and weighing the nongummy residue, the solubility was determined as 97.6%.

Example 2 Cotton fabric was soaked in a 5% aqueous solution of chloracetic acid containing 0.5% by weight of a sulfonated wetting agent, for about 2 minutes at 20 C., squeezed and then placed in a 30% aqueous solution of sodium hydroxide for about 1 minute at 49 C. The etherified fabric was then washed well with water, soured with acid to remove residual alkali and washed again with water. The material showed a degree of substitution of 0.025.

The etherified fabric was treated with an aqueous solution of chromic acid of 4% concentration at C. for about 1.5 minutes, washed with water and dried. The acid treated material was placed in a boiling aqueous solution of sodium hydroxide of 13.5% concentration,

solution of sodium hydroxide, of 97.8%.

giving a solubility of 85.9%. The residue was neither gummy or of gel-like consistency.

Example 3 Cotton fabric was carboxymethylated as in Example 2 except that the treatment with chloracetic acid was extended to 15 minutes and the treatment with the sodium hydroxide was at a temperature of 35 C. The thus etherified material had a degree of substitution of 0.017 and was treated with chromic acid as in Example 2. The acid modified material had a solubility of 79.2% in boiling 13.5% aqueous sodium hydroxide, leaving a residue in particle, non-gummy form.

Example 4 Cotton fabric was soaked in a 40% aqueous solution of chloracetic acid containing a small amount of wetting agent for minutes at 30 C. After squeezing the thus treated fabric, the same was placed in a 50% aqueous solution of sodium hydroxide for 2 minutes at 75 C. The etherified fabric was washed with water, soured with acid such as dilute sulfuric acid, and again washed. The etherified fabric had a degree of substitution of 0.23. The treated fabric was then placed in an aqueous solution containing by weight 3% sodium bichromate and 4% sulfuric acid, for 15 minutes at 35 C. The thus modified material had a solubility in a boiling 1.0% aqueous solution of sodium hydroxide, of 89.4% and there were no gummy residues in the solution.

Example 5 Cotton fabric was steeped in a 50% aqueous solution of sodium hydroxide at 75 for 5 minutes, squeezed and then placed in a 20% aqueous solution of chloracetic acid for 5 minutes at 75 C. The thus etherified fabric was further treated with an aqueous solution including 3% sodium bichromate and 4% sulfuric acid, for 1.5 minutes at 80 C., and then washed with water. In a boiling 13.5% aqueous solution of sodium hydroxide, the solubility of the acid modified fabric was 98.7%.

Example 6 Cotton linters was soaked in a 15% aqueous solution of chloracetic acid containing 0.5% of a wetting agent, for 5 minutes at 30 C. After squeezing, the treated linters were immersed in a 50% aqueous solution of sodium hydroxide for 5 minutes at 75 C. The etherified linters were washed with water, soured with acetic acid, again washed with water and then treated with an aqueous solution containing chromic acid, as set forth in Example 1. The acid modified carboxymethyl cellulose still retained their linter form and in a boiling 10.5% aqueous solution of sodium hydroxide, had a solubility of 96.9%.

The preceding example was repeated except that cotton threads were substituted for the linters. The resultant end product had a solubility in a boiling 10.5 aqueous The acid treated etherified material, prior to solution in the boiling alkali, retained its original thread form.

Example 7 .Water, dried and dissolved in a 0.1% aqueous solution of sodium hydroxide at boiling, giving a solubility of 98.6%. No gummy or gel-like residues were in the alkali solution of the acid modified material.

"The cellulose materials to be treated in accordance with-the instant invention maybe in the form of linters,

lprilp,.threads orfabricgand may be derived from cotton,

ramie, linen, jute, regenerated cellulose and the like. The conversion of the cellulose to the carboxymethyl form may be effected by the procedures well known in the art, utilizing the conventional etherifying agents to obtain a degree of substitution ranging from about 0.02 to about 2.5. In the case of the higher substituted, water soluble products, it is preferred that the same be converted to the acid form in a manner well known in the art, or converted to water insoluble salts such as the lead, copper, iron, silver or mercury salts of carboxymethyl cellulose.

The chromic acid or periodic acid treatment may involve the use of aqueous solutions of such acids or combinations of reagents forming the acid in situ, such treatment being effected at temperatures ranging from room temperature to boiling and at acid concentrations varying from about 0.5% to about-50%. A preferred range of acid concentrations is between about 3% to about 10%.

With higher acid concentrations, the impregnation interval is reduced and may be as little as a few seconds, the'treating temperature being correspondingly adjusted in inverse relation to said acid concentrations. On the other hand, with relatively low acid concentrations, the impregnating period is materially extended and may range up to about 24 hours, with an adjustment of the treating temperature upwardly.

In all cases, the conditions of the acid treatment of the etherified cellulose with chromic or periodic acid, are such as to leave the original physical form of the cellulose unchanged; the end product retaining a substantial portion of the strength of the untreated material. With the modified cellulose of the instant invention in fabric form, such treated fabric can be readily handled in reeling machines and other mechanical equipment required to utilize the same as a solubilized backing fabric for lace manufacture.

The acid modified carboxymethyl cellulose of the instant invention may be dissolved in alkaline solutions of a wide range of concentrations, being readily soluble in aqueous solutions of sodium hydroxide having a concentration of from about 0.01% to about 35.0%.

With carboxymethyl cellulose having a degree of substitution up to about 0.2 and treated with chromic or periodic acid, as described above, it is preferred to use an alkaline dissolving bath such as an aqueous solution of sodium hydroxide having a concentration of from about 4% to about 35%. When dissolving etherified cellulose having a degree of substitution greater than about 0.2 and acid treated in accordance with the invention, the concentration of the alkaline dissolving bath may be materially reduced and may be as low as about 0.01%. i

It is understood that in lieu of sodium hydroxide, other alkaline reagents may be used for dissolving the acid modified cellulose ether of the instant invention, including potassium hydroxide, lithium hydroxide, sodium carbonate, trisodium phosphate and the like.

As it is apparent that different embodimetns may be made within the spirit of the instant invention, it is to be understood that all matter herein described is to be deemed illustrative and not by way of limitation except as set forth in the appended claims.

Having thus described my invention, 1 claim as new and desire to protect by Letters Patent:

1. The process of forming chemically modified cellulose ccniprising impregnating carboxymethyl cellulose having from 0.02 to about 2.5 carboxymethyl groups per anhydroglucose unit, with an aqueous solution of an acid selected from the group consisting of chromic and periodic acids having a concentration of from about 0.5% to about 50% at a temperature of from room temperature to boiling for a period of from about a few seconds to 24 hours, the time and temperature of the acid impregnation being inversely related to the acid concentration,

to form an end product retaining the physical form and a major portion of the strength of said carboxymethyl cellulose and which is highly soluble in alkaline dissolving baths and free of gummy or gel-like residues as an incident to the solution thereof in said baths.

2. The process of claim 1 wherein the aqueous solution of acid has a concentration of from about 3% to about 10%.

3. The process of claim 1 wherein the carboxymethyl cellulose has not more than about 0.2 carboxymethyl groups per anhydroglucose unit, and said end product dissolves readily in aqueous solutions of sodium hydroxide having a concentration of from about 4% to about 35%.

4. The process of claim 1 wherein the carboxymethyl cellulose has more than 0.2 carboxymethyl groups per anhydroglucose unit, and said end product dissolves readily in aqueous solutions of sodium hydroxide having a concentration of about 0.01%.

5. The process of forming chemically modified cellulose comprising impregnating carboxymethylated cotton fabric having 0.02 carboxymethyl groups per anhydroglucose unit, with a 4% aqueous solution of chromic acid at 90 C. for about 1.5 minutes, washing the acid treated material with water and drying.

6. The process of forming chemically modified cellulose comprising impregnating carboxymethylated cellulose having about 0.5 carboxymethyl groups per anhydroglucose unit, with an aqueous solution of chromic acid for about 10 minutes at about 25 C., washing the acid treated material With water and drying.

7. Chemically modified cellulose comprising carboxymethyl cellulose having from 0.02 to about 2.5 carboxymethyl groups per anhydroglucose unit chemically modified with an acid selected from the group consisting of chromic and periodic acids in accordance with the process of claim 1, said acid modified carboxymethyl cellulose retaining the physical form and a major portion of the strength of the unmodified carboxymethyl cellulose, and having a solubility of from about 79.2% to about 98.6% in aklaline dissolving solutions, the insoluble residue being in discrete, non-gummy particle form.

References Cited in the file of this patent UNITED STATES PATENTS 2,278,612 Collings Apr. 7, 1942 2,422,572 Lilienfeld June 17, 1947 2,523,377 Klug Sept. 26, 1950 2,555,446 Hutchinson June 5, 1951 2,572,559 Chittum Oct. 23, 1951 2,724,632 Weisberg Nov. 22, 1955 2,724,633 Daul et al Nov. 22, 1955 2,749,336 Boddicker et a1 June 5, 1956 

1. THE PROCESS OF FORMING CHEMICALLY MODIFIED CELLULOSE COMPRISING IMPREGNATING CARBOXYMETHYL CELLULOSE HAVING FROM 0.02 TO ABOUT 2.5 CARBOXYMETHYL GROUPS PER ANHYDROGLUCOSE UNIT, WITH AN AQUEOUS SOLUTION OF AN ACID SELECTED FROM THE GROUP CONSISTING OF CHROMIC AND PERIODIC ACIDS HAVING A CONCENTRATION OF FROM ABOUT 0.5% TO ABOUT 50% AT A TEMPERATURE OF FROM ROOM TEMPERATURE TO BOILING FOR A PERIOD OF FROM ABOUT A FEW SECONDS TO 24 HOURS, THE TIME AND TEMPERATURE OF THE ACID IMPREGNATION BEING INVERSELY RELATED TO THE ACID CONCENTRATION, TO FORM AN END PRODUCT RETAINING THE PHYSICAL FORM AND A MAJOR PORTION OF THE STRENGTH OF SAID CARBOXYMETHYL CELLULOSE AND WHICH IS HIGHLY SOLUBLE IN ALKALINE DISSOLVING BATHS AND FREE OF GUMMY OR GEL-LIKE RESIDUES AS AN INCIDENT TO THE SOLUTION THEREOF IN SAID BATHS.
 7. CHEMICALLY MODIFIED CELLULOSE COMPRISING CARBOXYMETHYL CELLULOSE HAVING FROM 0.02 TO ABOUT 2.5 CARBOXYMETHYL GROUPS PER ANHYDROGLUCOSE UNIT CHEMICALLY MODIFIED WITH AN ACID SELECTED FROM THE GROUP CONSISTING OF CHROMIC AND PERIODIC ACIDS IN ACCORDANCE WITH THE PROCESS OF CLAIM 1, SAID ACID MODIFIED CARBOXYMETHYL CELLULOSE RETAINING THE PHYSICAL FORM AND A MAJOR PORTION OF THE STRENGTH OF THE UNMODIFIED CARBOXYMETHYL CELLULOSE, AND HAVING A SOLUBILITY OF FROM ABOUT 79.2% TO ABOUT 98.6% IN ALKALINE DISSOLVING SOLUTIONS, THE INSOLUBLE RESIDUE BEING IN DISCRETE, NON-GUMMY PARTICLE FORM. 